1. Field of the Invention
This invention relates in general to a smoke hatch and/or an explosion hatch and an emergency release latch mechanism for use with the hatch, and more particularly to release latch mechanisms for roof-mounted smoke hatches for buildings which hatches can be actuated by fire, pressure such as an explosion, manually and electrically and which, after actuation and opening of the hatch, the hatch may be closed and the release latch mechanism may be easily reset by a person at the periphery or end wall (curb) of the hatch.
2. Description of Related Art
Building smoke hatches are widely used for venting the inside of a building quickly to exhaust smoke or poisonous or explosive gas accumulated resulting from a fire in the building. As a rule, these hatches are not used as an entryway to a building. For safety purposes the cover or covers of the hatch are hinged and are heavily spring loaded to open position in order to effect rapid opening in a fire emergency, not only against their own weight but also against natural restraining forces such as wind or accumulated snow or ice. Since the cover areas are fairly large, the spring loading on the covers must be substantial to overcome these restraining forces. In addition, there are transitory uplift forces caused by wind passing over the covers, so that total door-opening forces may range for example from several hundred to as much as 1000 pounds or more per door in typical installations. Such preloads on the door or cover are opposed in the closed condition of the hatch cover solely by the latch mechanism employed. The unit forces acting in the latching dog and shackle members are accordingly exceedingly high, making it a problem to provide an arrangement which is capable of securely latching the cover in closed condition, yet which requires only a minimum force to effect release upon occurrence of a fire or explosion.
It is common practice in the prior art to effect automatic release of the latch and consequent opening of the hatch cover in case of fire emergency by employing devices incorporating a low melting point fusible metal link which automatically ruptures upon attainment of a predetermined elevated ambient temperature as a result of a fire in the building. Attempts to employ fusible links directly connected to the hatch cover are generally unsatisfactory where, as indicated above, the preload forces on the cover are of such high order which are greater than the strength of the fusible links. The fusible links are made of a low melting or fusing temperature metal to be effective for fire detection purposes but inherently lack the necessary tensile strength to continuously resist the heavy preload forces of the doors in the closed position. Realizing such drawbacks, hatches have been made heretofore to provide an emergency release device which will withstand the high loading on the latch mechanism without adversely affecting the temperature at which it is set to release in case of a building fire. Such a release latch mechanism is shown in U.S. Pat. No. 3,516,198 to Lyons and assigned to the assignee of the present invention and which patent is herein incorporated by reference. The latch mechanism shown in Lyons reduces the unit forces acting on the fusible link or other emergency-actuated release element. These hatches are also made for allowing the hatch cover or covers to open in case of an explosion within the building. These type hatches generally require a multistep latch mechanism resetting procedure performed by a person reaching out over the open hatch to the latch mechanism positioned at the center of the hatch.
Bearing in mind the problems and deficiencies of the prior art, it is therefore an object of the present invention to provide an emergency release latch mechanism for heavily spring biased covers of smoke hatches and the like, which effectively reduces the unit forces acting on an emergency-actuated release element itself, e.g., a fusible link, yet is compact and mechanically simple and certain in operation and which latch mechanism may easily be set or reset after actuation by a person positioned at the periphery of the hatch without having to extend or reach out over the opening.
Another object is to provide a release latch mechanism of the character described which permits manual release of the latch cover without disrupting the fusible link element or other automatic emergency-actuated release member, so that upon reclosing the hatch cover and re-engagement of the latch mechanism, such emergency-actuated release member is again automatically effective.
A further object of the novel latch mechanism here disclosed is to provide a latch mechanism which may be readily operated in tandem with another mechanism of identical construction, both being under the control of a single emergency-actuated release element, where it is desired to employ two or more latch means on the same door or cover, or where the hatch employs a double door each having at least one emergency release latch mechanism.
Another object of the present invention is to provide a smoke hatch employing the emergency release latch mechanism of the invention.
Still other objects and advantages of the invention will in part be obvious and will in part be apparent from the specification.
The invention is illustrated for convenience in the embodiment of a latch mechanism for double doored vent or smoke hatch construction shown in the accompanying drawings.